In recent years, amid calls for environmental issues, move to paperless offices has been promoted. Hence, a document management system that scans paper documents accumulated and saved using binders or the like using a scanner, converts scanned document images into portable document format (to be abbreviated as “PDF” hereinafter) data, and accumulates and saves in an image storage device (database) has been conventionally developed.
On the other hand, some digital multi-function peripherals (to be abbreviated as “MFP” hereinafter) with expanded functions record pointer information in the image storage device that stores the corresponding image on a cover page or description information of a paper document as additional information upon printing and outputting that image (image data) as a paper document. When the paper document formed by recording that image is to be copied, the storage location in the image storage device that stores an original image is detected from the pointer information appended to the cover page or the like, and the original image stored in the image storage device can be directly used in an edit process and re-print process in place of the image scanned from the paper document. As a result, paper documents themselves need not be saved, and problems such as deterioration of image quality and the like due to very often re-uses of images scanned from paper documents can be prevented (for example, see patent reference 1: Japanese Patent Laid-Open No. 10-143414).
The former technique can save a paper document as a PDF file with a compact information volume. However, since the entire file is saved as one image data, it is difficult to partially retrieve and re-use a given object in the document. Therefore, in order to re-use such data, graphics, tables, and the like must be created again using application software.
The latter technique can directly access an original digital file corresponding to an output paper document, thus allowing easy re-use and re-edit processes. However, this technique cannot cope with externally acquired new documents and old paper documents whose original digital files cannot be located. Hence, upon scanning a document, if a corresponding digital file is already available, it can be efficiently retrieved. However, if no such file is available, such document must be efficiently converted into and saved as vector data to allow the next and subsequent retrieval processes.